Mantis shrimp has one of nature’s most powerful and lightning-fast punches – it’s on par with the force generated by a .22 caliber bullet. This makes the creature an attractive object of study for scientists keen to learn more about relevant biomechanics. Among other uses, this could lead to small robots capable of equally fast and powerful movements. Today, a team of researchers from Harvard University has developed a new biomechanical model for the mantis shrimp mighty appendage, and he built a little robot to mimic this movement, according to a recent article published in the Proceedings of the National Academy of Sciences.
“We are fascinated by so many remarkable behaviors that we see in nature, especially when those behaviors meet or exceed what can be achieved by human-made devices. ” said lead author Robert Wood, roboticist at the John A. Paulson School of Engineering and Applied Sciences (SEAS) at Harvard University. “The speed and force of mantis shrimp strikes, for example, are the result of a complex underlying mechanism. By building a robotic model of an appendix striking a mantis shrimp, we are able to study these mechanisms in unprecedented detail. “
Wood’s research group made headlines several years ago when he built RoboBee, a small robot able to fly partially without attachment. The ultimate goal of this initiative is to build a swarm of tiny interconnected robots capable of sustained, unattached flight, a significant technological challenge, given the scale of the size of the insects, which alters the different forces at play. 2019, the Wood’s group announced its achievement the lightest insect scale robot to date to achieve sustained, unattached flight – an upgraded version called the RoboBee X-Wing. (Kenny Breuer, writing in Nature, described it as “a tour de force of system design and engineering.”)
Now Wood’s group has turned their attention to the biomechanics of the mantis shrimp punch. As we reported previously, mantis shrimp come in many varieties; there are about 450 known species. But they can generally be grouped into two types: those that stab their prey with spear-shaped appendages (“launchers”) and those that crush their prey (“breakers”) with large, rounded, hammer-shaped claws (” raptor appendages “). These strikes are so fast (up to 23 meters per second, or 51 mph) and powerful, that they often produce cavitating bubbles in the water, creating a shock wave that can serve as a follow-up strike, stunning and sometimes killing the prey. Sometimes a hit can even produce sonoluminescence, with the cavitating bubbles producing a brief flash of light as they collapse.
According to a 2018 study, the secret to this powerful punch seems to come not from the bulky muscles but from the spring-loaded anatomical structure of the shrimp’s arms, similar to a bow and arrows or a mousetrap. The muscles of the shrimp pull on a saddle-like structure in the arm, causing it to bend and store potential energy, which is released with the sway of the club-shaped claw. It is basically a latch-type mechanism (technically, latch-mediated spring actuation, or LaMSA), with small structures in muscle tendons called sclerites acting as a latch.
This is well understood, and there are several other small organisms capable of producing super-fast movements thanks to a similar locking mechanism: the legs of frogs and the tongues of chameleons, for example, as well as the mandibles of ants with trap jaws. and the seeds of exploding plants. . But biologists who have studied these mechanisms for years have noticed something unusual in mantis shrimp: a millisecond delay between the time the unlocking and hooking action occurs.
“When you watch the typing process on a high-speed camera, there is a delay between when the sclerites release and the appendix fires,” said co-lead author Nak-seung (Patrick) Hyun, postdoctoral fellow at SEAS. “It’s like a mouse was triggering a mousetrap, but instead of immediately clicking, there was a noticeable delay before it did click. There is obviously another mechanism that holds the appendix in place, but no one has been able to understand analytically how the other mechanism works.